Molding high-pressure system

Large machines operate best when a hybrid clamping system Is used. Here one uses large volume, low pressure hydraulics to activate the toggle system and close the mold. Once the mold Is virtually closed, a low volume, high pressure system applies the clamping force (see Figure 2). 

In compression molding, high pressures are applied at the mold, frequently hampering dimension stability of the product, mainly when more elements are introduced. In the method of transfer molding, the system com-... 

In the reinforced RIM (RRIM) process a dry reinforcement preform is placed in a closed mold. Next a reactive plastic system is mixed under high pressure in a specially designed mixing head. Upon mixing, the reacting liquid flows at low pressure through a runner system to fill the mold cavity, impregnating the reinforcement in the process. Once the mold cavity is filled, the plastic quickly completes its reaction. The complete cycle time required to produce a molded thick product can be as little as one minute. 

Processing equipment consists of the material conditioning system, the high-pressure metering system, the mixing head, and the mold carrier. Since the RIM process involves a chemical reaction in the mold after the intermediates have been mixed, it is necessary, if consistent parts are to be produced, that the material delivered to the mix head be consistent from shot to shot. 

The heart of the system is the mixing chamber, where the liquid components must be thoroughly mixed without imparting turbulence. High-volume, high-pressure recirculating pumps from liquid-storage tanks accomplish continuous delivery of the components to the mold. Automatic controls are used to maintain precise flow and temperature of the plastic. 

There are a number of different systems and machines available for producing structural foams. The most important categories are low-pressure molding and high-pressure molding. Low-pressure molding... 

Foam-Kon. [LNP ICI Advanced Materials] Thermoplastic structural foam cone. for high pressure foam systems, inj. molding compds. 

Wet- and dry-bag are two techniques for isostatic molding which are principally identical but operationally different. The wet-bag process is similar to the basic molding procedure in which the mold is submerged in the pressurization fluid. In the dry-bag technique, the mold and the bag are fixed in place and the functions of the mold and the pressurization vessel are combined. The pressurization fluid is introduced through a high-pressure liquid supply system behind the flexible bag (Fig. 5.17). The mold assembly is designed to withstand this pressure. The term dry-bag contrasts the absence of submerged mold and wet mold assembly. 

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